This invention relates to motor safety switches of which various designs are known. Typically, such motor protection consists of a relay or contactor associated with a thermal protection mechanism. Accordingly, both the entire contact making system and the magnetic system which actuates the contact system, and the associated thermal protection system, are mounted within a single housing of a specific design. The thermal protection system or mechanism is tripped only when the current load or the thermal load exceeds a given value. In practice, this thermal protection mechanism for the motor operates relatively inertly, because the current load or the thermal load increases quite slowly most of the time. In order to protect a particular electric motor against abrupt electrical interruptions, such as shorts, a separate cut-off is required which heretofore has been mounted in a separate housing outside of the conventional contact housing. Generally a total of eighteeen connections are required for the electrical hook-ups between these separate units. An ordinary circuit breaker is also known which includes a contacting system and a magnetic system connected by means of electric conductors to a separate motor protection switch. This construction requires a total of twelve connections each hooked up to a particular electrical line.
In both of the aforementioned designs the wiring is complex, time consuming, and the material expenditure required both for the electric wiring and the many hook-ups to the different equipment is inordinately high. Furthermore, because of the necessity of extraneous exterior wiring, the space required is increased, thus necessitating a relatively large switch gear cabinet and its attendant higher costs.
Other conventional motor safety or protection systems are known, but these generally vary across a large spectrum of particular components depending upon the intended specific application.
A final typical motor protection system is of the known contactor type in which typical cut off means and the associated accessory contact system are integrated into a single assembly. cSUMMARY OF THE INVENTION
The present invention is based upon the recognition that there is a different demand in practice with respect to motor protecting switches or motor safety switches, depending upon particular circumstances. Illustratively, in a few cases only one switch mechanism with a single contact system is required which can be simply turned on and off manually. In such a case, however, the motor protection must be guaranteed for all types of electrical loads. In another system, at a minimum the contact system must be turned on by means of an electromagnet. As another example, motor protecting switches are needed under electrical requirements of one contacting system, one electromagnetic drive and one accessory contact system with the motor protection being assured for every operational eventuality. Obviously, due to these different requirements there are then numerous different designs, and according to the present invention numerous independent components establishing a particular motor safety switch is provided in the absence of eccessive expenditures of money or wiring, material and/or labor. The overall motor safety switch is compact when assembled, can be readily adapted to practically all requirements, can be assembled componentwise as need be without the necessity of maintaining large stocks of items in hand, and the various components, subassemblies and total assemblies thereof are readily interengageable and mutually exchangeable.
In accordance with the present invention a motor safety switch is provided through a series of independent components, namely, a switch unit consisting of a contact system, a thermal tripper and a magnetic tripper; an electromagnetic drive unit and a modular contact unit, all readily maintained in assembled modular relationship. In this manner, one obtains the essential advantage that the individual components are virtually always identical, can be mass produced regardless of what the final configuration of the motor safety switch might be, and in this way the main cost for a particular job requirement is drastically reduced. It should be clear that the individually different motor safety switches for different purposes will make use of only a few different and less costly parts, such as base plates and/or covers, pushbuttons, possibly junction numbers, while the main components are essentially universal for virtually any application. Thus, the different small parts do not represent high manufacturing costs and can be readily assembled to the main major components without undue loss of time, particularly through advantageously provided mechanical connectors and quick couplings of the present invention. Obviously, since the independent components can be assembled into different varieties of motor safety switches, there if no need for stocking large quantities of differently constructed motor safety switches, and instead smaller quantities of basic main components can be stocked and selectively utilized as need be to satisfy a particular requirement by simply constructing a desired motor safety switch therefrom.
In order to reduce the overall size of the motor safety switches which can be constructed from assembled independent components pursuant to this invention, the independent individual components are preferably stacked upon each other perpendicularly to a mounting plane or surface of an associated switch cabinet or the like. When appropriately connected by mechanical connecting means and so assembled, there is generally sufficient space for any stacked number of independent components, simply because most switch cabinets have space available perpendicular to the mounting plane, whereas there is very little space available in the other two coordinates parallel to the mounting plane. The latter occurs because normally conventional devices are mounted in series tightly next to one another and above each other, all of which resulted in the previously noted disadvantages of conventional motor protection switches. However, the latter disadvantage is totally overcome by the perpendicular stacking of the components of the present invention. Furthermore, in keeping with the invention, the individual components or subassemblies are preferably of the same width and as standardized as possible.